The present invention relates to multi-speed hubs for bicycles and more particular to a bicycle multi-speed hub having first, second and third planetary gear mechanisms that are configured to be controlled exclusively by pawls.
DE 197 45 419 A1 discloses a multi-speed hub for a bicycle that includes a hub shaft, a driver and a hub shell rotatably mounted on the hub shaft. To provide multiple gear ratios between the driver and the hub shell, the multi-speed hub includes a planetary gearing system. The planetary gearing system includes two planetary gear mechanisms that are associated with a shifting device or control device for selecting a desired gear ratio. A sun gear of the first planetary gearing system is joined nonrotatably to the hub shaft. The shifting device includes three coupling elements rotatable about the hub shaft and are couplable with different parts of the planetary gear mechanisms to select the desired gear ratio.
There is a need to refine the above described multi-speed hub by using pawls to join all of the elements participating in torque transfer to achieve a rapid gear change without delay. Further it would be advantageous to have some of the pawls work as automatic pawls, i.e. always engaged and are overrun when the bicycle is coasting (pedals are stationary) or bypassed when the torque path passes through other elements of the system. Also it is desirable to have the shifting device arranged on one side of the multi-speed hub and have it occupy as little space as possible. Still further, it is advantageous to move the controllable pawls by shifting elements that are arranged around the hub shaft and are joined to the shifting device, resulting in the elements of the two planetary gear mechanisms nonrotatably arranged on the hub shaft, in particular a first sun gear of the first planetary gear mechanism, may be fitted on and detachably joined to the hub shaft.